[deliverable/linux.git] / block / blk-merge.c

/*
 * Functions related to segment and merge handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>

#include "blk.h"

void blk_recalc_rq_sectors(struct request *rq, int nsect)
{
	if (blk_fs_request(rq) || blk_discard_rq(rq)) {
		rq->hard_sector += nsect;
		rq->hard_nr_sectors -= nsect;

		/*
		 * Move the I/O submission pointers ahead if required.
		 */
		if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
		    (rq->sector <= rq->hard_sector)) {
			rq->sector = rq->hard_sector;
			rq->nr_sectors = rq->hard_nr_sectors;
			rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
			rq->current_nr_sectors = rq->hard_cur_sectors;
			rq->buffer = bio_data(rq->bio);
		}

		/*
		 * if total number of sectors is less than the first segment
		 * size, something has gone terribly wrong
		 */
		if (rq->nr_sectors < rq->current_nr_sectors) {
			printk(KERN_ERR "blk: request botched\n");
			rq->nr_sectors = rq->current_nr_sectors;
		}
	}
}

void blk_recalc_rq_segments(struct request *rq)
{
	int nr_phys_segs;
	int nr_hw_segs;
	unsigned int phys_size;
	unsigned int hw_size;
	struct bio_vec *bv, *bvprv = NULL;
	int seg_size;
	int hw_seg_size;
	int cluster;
	struct req_iterator iter;
	int high, highprv = 1;
	struct request_queue *q = rq->q;

	if (!rq->bio)
		return;

	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
	hw_seg_size = seg_size = 0;
	phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
	rq_for_each_segment(bv, rq, iter) {
		/*
		 * the trick here is making sure that a high page is never
		 * considered part of another segment, since that might
		 * change with the bounce page.
		 */
		high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
		if (high || highprv)
			goto new_hw_segment;
		if (cluster) {
			if (seg_size + bv->bv_len > q->max_segment_size)
				goto new_segment;
			if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
				goto new_segment;
			if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
				goto new_segment;
			if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
				goto new_hw_segment;

			seg_size += bv->bv_len;
			hw_seg_size += bv->bv_len;
			bvprv = bv;
			continue;
		}
new_segment:
		if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
		    !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
			hw_seg_size += bv->bv_len;
		else {
new_hw_segment:
			if (nr_hw_segs == 1 &&
			    hw_seg_size > rq->bio->bi_hw_front_size)
				rq->bio->bi_hw_front_size = hw_seg_size;
			hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
			nr_hw_segs++;
		}

		nr_phys_segs++;
		bvprv = bv;
		seg_size = bv->bv_len;
		highprv = high;
	}

	if (nr_hw_segs == 1 &&
	    hw_seg_size > rq->bio->bi_hw_front_size)
		rq->bio->bi_hw_front_size = hw_seg_size;
	if (hw_seg_size > rq->biotail->bi_hw_back_size)
		rq->biotail->bi_hw_back_size = hw_seg_size;
	rq->nr_phys_segments = nr_phys_segs;
	rq->nr_hw_segments = nr_hw_segs;
}

void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
	struct request rq;
	struct bio *nxt = bio->bi_next;
	rq.q = q;
	rq.bio = rq.biotail = bio;
	bio->bi_next = NULL;
	blk_recalc_rq_segments(&rq);
	bio->bi_next = nxt;
	bio->bi_phys_segments = rq.nr_phys_segments;
	bio->bi_hw_segments = rq.nr_hw_segments;
	bio->bi_flags |= (1 << BIO_SEG_VALID);
}
EXPORT_SYMBOL(blk_recount_segments);

static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
				   struct bio *nxt)
{
	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
		return 0;

	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
		return 0;

	if (!bio_has_data(bio))
		return 1;

	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
		return 0;

	/*
	 * bio and nxt are contiguous in memory; check if the queue allows
	 * these two to be merged into one
	 */
	if (BIO_SEG_BOUNDARY(q, bio, nxt))
		return 1;

	return 0;
}

static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio,
				 struct bio *nxt)
{
	if (!bio_flagged(bio, BIO_SEG_VALID))
		blk_recount_segments(q, bio);
	if (!bio_flagged(nxt, BIO_SEG_VALID))
		blk_recount_segments(q, nxt);
	if (bio_has_data(bio) &&
	    (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
	     BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size)))
		return 0;
	if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
		return 0;

	return 1;
}

/*
 * map a request to scatterlist, return number of sg entries setup. Caller
 * must make sure sg can hold rq->nr_phys_segments entries
 */
int blk_rq_map_sg(struct request_queue *q, struct request *rq,
		  struct scatterlist *sglist)
{
	struct bio_vec *bvec, *bvprv;
	struct req_iterator iter;
	struct scatterlist *sg;
	int nsegs, cluster;

	nsegs = 0;
	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);

	/*
	 * for each bio in rq
	 */
	bvprv = NULL;
	sg = NULL;
	rq_for_each_segment(bvec, rq, iter) {
		int nbytes = bvec->bv_len;

		if (bvprv && cluster) {
			if (sg->length + nbytes > q->max_segment_size)
				goto new_segment;

			if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
				goto new_segment;
			if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
				goto new_segment;

			sg->length += nbytes;
		} else {
new_segment:
			if (!sg)
				sg = sglist;
			else {
				/*
				 * If the driver previously mapped a shorter
				 * list, we could see a termination bit
				 * prematurely unless it fully inits the sg
				 * table on each mapping. We KNOW that there
				 * must be more entries here or the driver
				 * would be buggy, so force clear the
				 * termination bit to avoid doing a full
				 * sg_init_table() in drivers for each command.
				 */
				sg->page_link &= ~0x02;
				sg = sg_next(sg);
			}

			sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
			nsegs++;
		}
		bvprv = bvec;
	} /* segments in rq */


	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
	    (rq->data_len & q->dma_pad_mask)) {
		unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;

		sg->length += pad_len;
		rq->extra_len += pad_len;
	}

	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
		if (rq->cmd_flags & REQ_RW)
			memset(q->dma_drain_buffer, 0, q->dma_drain_size);

		sg->page_link &= ~0x02;
		sg = sg_next(sg);
		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
			    q->dma_drain_size,
			    ((unsigned long)q->dma_drain_buffer) &
			    (PAGE_SIZE - 1));
		nsegs++;
		rq->extra_len += q->dma_drain_size;
	}

	if (sg)
		sg_mark_end(sg);

	return nsegs;
}
EXPORT_SYMBOL(blk_rq_map_sg);

static inline int ll_new_mergeable(struct request_queue *q,
				   struct request *req,
				   struct bio *bio)
{
	int nr_phys_segs = bio_phys_segments(q, bio);

	if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}

	/*
	 * A hw segment is just getting larger, bump just the phys
	 * counter.
	 */
	req->nr_phys_segments += nr_phys_segs;
	return 1;
}

static inline int ll_new_hw_segment(struct request_queue *q,
				    struct request *req,
				    struct bio *bio)
{
	int nr_hw_segs = bio_hw_segments(q, bio);
	int nr_phys_segs = bio_phys_segments(q, bio);

	if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
	    || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}

	/*
	 * This will form the start of a new hw segment.  Bump both
	 * counters.
	 */
	req->nr_hw_segments += nr_hw_segs;
	req->nr_phys_segments += nr_phys_segs;
	return 1;
}

int ll_back_merge_fn(struct request_queue *q, struct request *req,
		     struct bio *bio)
{
	unsigned short max_sectors;
	int len;

	if (unlikely(blk_pc_request(req)))
		max_sectors = q->max_hw_sectors;
	else
		max_sectors = q->max_sectors;

	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}
	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
		blk_recount_segments(q, req->biotail);
	if (!bio_flagged(bio, BIO_SEG_VALID))
		blk_recount_segments(q, bio);
	len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
	if (!bio_has_data(bio) || 
	    (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))
	     && !BIOVEC_VIRT_OVERSIZE(len))) {
		int mergeable =  ll_new_mergeable(q, req, bio);

		if (mergeable) {
			if (req->nr_hw_segments == 1)
				req->bio->bi_hw_front_size = len;
			if (bio->bi_hw_segments == 1)
				bio->bi_hw_back_size = len;
		}
		return mergeable;
	}

	return ll_new_hw_segment(q, req, bio);
}

int ll_front_merge_fn(struct request_queue *q, struct request *req,
		      struct bio *bio)
{
	unsigned short max_sectors;
	int len;

	if (unlikely(blk_pc_request(req)))
		max_sectors = q->max_hw_sectors;
	else
		max_sectors = q->max_sectors;


	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}
	len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
	if (!bio_flagged(bio, BIO_SEG_VALID))
		blk_recount_segments(q, bio);
	if (!bio_flagged(req->bio, BIO_SEG_VALID))
		blk_recount_segments(q, req->bio);
	if (!bio_has_data(bio) || 
	    (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
	     !BIOVEC_VIRT_OVERSIZE(len))) {
		int mergeable =  ll_new_mergeable(q, req, bio);

		if (mergeable) {
			if (bio->bi_hw_segments == 1)
				bio->bi_hw_front_size = len;
			if (req->nr_hw_segments == 1)
				req->biotail->bi_hw_back_size = len;
		}
		return mergeable;
	}

	return ll_new_hw_segment(q, req, bio);
}

static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
				struct request *next)
{
	int total_phys_segments;
	int total_hw_segments;

	/*
	 * First check if the either of the requests are re-queued
	 * requests.  Can't merge them if they are.
	 */
	if (req->special || next->special)
		return 0;

	/*
	 * Will it become too large?
	 */
	if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
		return 0;

	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
	if (blk_phys_contig_segment(q, req->biotail, next->bio))
		total_phys_segments--;

	if (total_phys_segments > q->max_phys_segments)
		return 0;

	total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
	if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
		int len = req->biotail->bi_hw_back_size +
				next->bio->bi_hw_front_size;
		/*
		 * propagate the combined length to the end of the requests
		 */
		if (req->nr_hw_segments == 1)
			req->bio->bi_hw_front_size = len;
		if (next->nr_hw_segments == 1)
			next->biotail->bi_hw_back_size = len;
		total_hw_segments--;
	}

	if (total_hw_segments > q->max_hw_segments)
		return 0;

	/* Merge is OK... */
	req->nr_phys_segments = total_phys_segments;
	req->nr_hw_segments = total_hw_segments;
	return 1;
}

/*
 * Has to be called with the request spinlock acquired
 */
static int attempt_merge(struct request_queue *q, struct request *req,
			  struct request *next)
{
	if (!rq_mergeable(req) || !rq_mergeable(next))
		return 0;

	/*
	 * not contiguous
	 */
	if (req->sector + req->nr_sectors != next->sector)
		return 0;

	if (rq_data_dir(req) != rq_data_dir(next)
	    || req->rq_disk != next->rq_disk
	    || next->special)
		return 0;

	if (blk_integrity_rq(req) != blk_integrity_rq(next))
		return 0;

	/*
	 * If we are allowed to merge, then append bio list
	 * from next to rq and release next. merge_requests_fn
	 * will have updated segment counts, update sector
	 * counts here.
	 */
	if (!ll_merge_requests_fn(q, req, next))
		return 0;

	/*
	 * At this point we have either done a back merge
	 * or front merge. We need the smaller start_time of
	 * the merged requests to be the current request
	 * for accounting purposes.
	 */
	if (time_after(req->start_time, next->start_time))
		req->start_time = next->start_time;

	req->biotail->bi_next = next->bio;
	req->biotail = next->biotail;

	req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;

	elv_merge_requests(q, req, next);

	if (req->rq_disk) {
		struct hd_struct *part
			= get_part(req->rq_disk, req->sector);
		disk_round_stats(req->rq_disk);
		req->rq_disk->in_flight--;
		if (part) {
			part_round_stats(part);
			part->in_flight--;
		}
	}

	req->ioprio = ioprio_best(req->ioprio, next->ioprio);

	__blk_put_request(q, next);
	return 1;
}

int attempt_back_merge(struct request_queue *q, struct request *rq)
{
	struct request *next = elv_latter_request(q, rq);

	if (next)
		return attempt_merge(q, rq, next);

	return 0;
}

int attempt_front_merge(struct request_queue *q, struct request *rq)
{
	struct request *prev = elv_former_request(q, rq);

	if (prev)
		return attempt_merge(q, prev, rq);

	return 0;
}
Commit	Line	Data
d6d48196 JA	1	/*
	2	* Functions related to segment and merge handling
	3	*/
	4	#include <linux/kernel.h>
	5	#include <linux/module.h>
	6	#include <linux/bio.h>
	7	#include <linux/blkdev.h>
	8	#include <linux/scatterlist.h>
	9
	10	#include "blk.h"
	11
	12	void blk_recalc_rq_sectors(struct request *rq, int nsect)
	13	{
e17fc0a1	14	if (blk_fs_request(rq) \|\| blk_discard_rq(rq)) {
d6d48196 JA	15	rq->hard_sector += nsect;
	16	rq->hard_nr_sectors -= nsect;
	17
	18	/*
	19	* Move the I/O submission pointers ahead if required.
	20	*/
	21	if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
	22	(rq->sector <= rq->hard_sector)) {
	23	rq->sector = rq->hard_sector;
	24	rq->nr_sectors = rq->hard_nr_sectors;
	25	rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
	26	rq->current_nr_sectors = rq->hard_cur_sectors;
	27	rq->buffer = bio_data(rq->bio);
	28	}
	29
	30	/*
	31	* if total number of sectors is less than the first segment
	32	* size, something has gone terribly wrong
	33	*/
	34	if (rq->nr_sectors < rq->current_nr_sectors) {
6728cb0e	35	printk(KERN_ERR "blk: request botched\n");
d6d48196 JA	36	rq->nr_sectors = rq->current_nr_sectors;
	37	}
	38	}
	39	}
	40
	41	void blk_recalc_rq_segments(struct request *rq)
	42	{
	43	int nr_phys_segs;
	44	int nr_hw_segs;
	45	unsigned int phys_size;
	46	unsigned int hw_size;
	47	struct bio_vec bv, bvprv = NULL;
	48	int seg_size;
	49	int hw_seg_size;
	50	int cluster;
	51	struct req_iterator iter;
	52	int high, highprv = 1;
	53	struct request_queue *q = rq->q;
	54
	55	if (!rq->bio)
	56	return;
	57
75ad23bc	58	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	59	hw_seg_size = seg_size = 0;
	60	phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
	61	rq_for_each_segment(bv, rq, iter) {
	62	/*
	63	* the trick here is making sure that a high page is never
	64	* considered part of another segment, since that might
	65	* change with the bounce page.
	66	*/
	67	high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
	68	if (high \|\| highprv)
	69	goto new_hw_segment;
	70	if (cluster) {
	71	if (seg_size + bv->bv_len > q->max_segment_size)
	72	goto new_segment;
	73	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
	74	goto new_segment;
	75	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
	76	goto new_segment;
	77	if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
	78	goto new_hw_segment;
	79
	80	seg_size += bv->bv_len;
	81	hw_seg_size += bv->bv_len;
	82	bvprv = bv;
	83	continue;
	84	}
	85	new_segment:
	86	if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
	87	!BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
	88	hw_seg_size += bv->bv_len;
	89	else {
	90	new_hw_segment:
	91	if (nr_hw_segs == 1 &&
	92	hw_seg_size > rq->bio->bi_hw_front_size)
	93	rq->bio->bi_hw_front_size = hw_seg_size;
	94	hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
	95	nr_hw_segs++;
	96	}
	97
	98	nr_phys_segs++;
	99	bvprv = bv;
	100	seg_size = bv->bv_len;
	101	highprv = high;
	102	}
	103
	104	if (nr_hw_segs == 1 &&
	105	hw_seg_size > rq->bio->bi_hw_front_size)
	106	rq->bio->bi_hw_front_size = hw_seg_size;
	107	if (hw_seg_size > rq->biotail->bi_hw_back_size)
	108	rq->biotail->bi_hw_back_size = hw_seg_size;
	109	rq->nr_phys_segments = nr_phys_segs;
	110	rq->nr_hw_segments = nr_hw_segs;
	111	}
	112
	113	void blk_recount_segments(struct request_queue q, struct bio bio)
	114	{
	115	struct request rq;
	116	struct bio *nxt = bio->bi_next;
	117	rq.q = q;
	118	rq.bio = rq.biotail = bio;
	119	bio->bi_next = NULL;
	120	blk_recalc_rq_segments(&rq);
	121	bio->bi_next = nxt;
	122	bio->bi_phys_segments = rq.nr_phys_segments;
123	bio->bi_hw_segments = rq.nr_hw_segments;
124	bio->bi_flags \|= (1 << BIO_SEG_VALID);
125	}
126	EXPORT_SYMBOL(blk_recount_segments);
127
128	static int blk_phys_contig_segment(struct request_queue q, struct bio bio,
129	struct bio *nxt)
130	{
75ad23bc	131	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
d6d48196 JA	132	return 0;
d6d48196 JA	133
d6d48196 JA	134	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
	135	return 0;
	136
e17fc0a1 DW	137	if (!bio_has_data(bio))
	138	return 1;
	139
	140	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
	141	return 0;
	142
d6d48196	143	/*
e17fc0a1	144	* bio and nxt are contiguous in memory; check if the queue allows
d6d48196 JA	145	* these two to be merged into one
	146	*/
	147	if (BIO_SEG_BOUNDARY(q, bio, nxt))
	148	return 1;
	149
	150	return 0;
	151	}
	152
	153	static int blk_hw_contig_segment(struct request_queue q, struct bio bio,
	154	struct bio *nxt)
	155	{
2cdf79ca	156	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	157	blk_recount_segments(q, bio);
2cdf79ca	158	if (!bio_flagged(nxt, BIO_SEG_VALID))
d6d48196	159	blk_recount_segments(q, nxt);
e17fc0a1 DW	160	if (bio_has_data(bio) &&
	161	(!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) \|\|
	162	BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size)))
d6d48196 JA	163	return 0;
	164	if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
	165	return 0;
	166
	167	return 1;
	168	}
	169
	170	/*
	171	* map a request to scatterlist, return number of sg entries setup. Caller
	172	* must make sure sg can hold rq->nr_phys_segments entries
	173	*/
	174	int blk_rq_map_sg(struct request_queue q, struct request rq,
	175	struct scatterlist *sglist)
	176	{
	177	struct bio_vec bvec, bvprv;
	178	struct req_iterator iter;
	179	struct scatterlist *sg;
	180	int nsegs, cluster;
	181
	182	nsegs = 0;
75ad23bc	183	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	184
	185	/*
	186	* for each bio in rq
	187	*/
	188	bvprv = NULL;
	189	sg = NULL;
	190	rq_for_each_segment(bvec, rq, iter) {
	191	int nbytes = bvec->bv_len;
	192
	193	if (bvprv && cluster) {
	194	if (sg->length + nbytes > q->max_segment_size)
	195	goto new_segment;
	196
	197	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
	198	goto new_segment;
	199	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
	200	goto new_segment;
	201
	202	sg->length += nbytes;
	203	} else {
	204	new_segment:
	205	if (!sg)
	206	sg = sglist;
	207	else {
	208	/*
	209	* If the driver previously mapped a shorter
	210	* list, we could see a termination bit
	211	* prematurely unless it fully inits the sg
	212	* table on each mapping. We KNOW that there
	213	* must be more entries here or the driver
	214	* would be buggy, so force clear the
	215	* termination bit to avoid doing a full
	216	* sg_init_table() in drivers for each command.
	217	*/
	218	sg->page_link &= ~0x02;
	219	sg = sg_next(sg);
	220	}
	221
	222	sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
	223	nsegs++;
	224	}
	225	bvprv = bvec;
	226	} /* segments in rq */
	227
f18573ab FT	228
	229	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
	230	(rq->data_len & q->dma_pad_mask)) {
	231	unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
	232
	233	sg->length += pad_len;
	234	rq->extra_len += pad_len;
	235	}
	236
2fb98e84	237	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
db0a2e00 TH	238	if (rq->cmd_flags & REQ_RW)
	239	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
	240
d6d48196 JA	241	sg->page_link &= ~0x02;
	242	sg = sg_next(sg);
	243	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	244	q->dma_drain_size,
	245	((unsigned long)q->dma_drain_buffer) &
	246	(PAGE_SIZE - 1));
	247	nsegs++;
7a85f889	248	rq->extra_len += q->dma_drain_size;
d6d48196 JA	249	}
	250
	251	if (sg)
	252	sg_mark_end(sg);
	253
	254	return nsegs;
	255	}
d6d48196 JA	256	EXPORT_SYMBOL(blk_rq_map_sg);
	257
	258	static inline int ll_new_mergeable(struct request_queue *q,
	259	struct request *req,
	260	struct bio *bio)
	261	{
	262	int nr_phys_segs = bio_phys_segments(q, bio);
	263
	264	if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	265	req->cmd_flags \|= REQ_NOMERGE;
	266	if (req == q->last_merge)
	267	q->last_merge = NULL;
	268	return 0;
	269	}
	270
	271	/*
	272	* A hw segment is just getting larger, bump just the phys
	273	* counter.
	274	*/
	275	req->nr_phys_segments += nr_phys_segs;
	276	return 1;
	277	}
	278
	279	static inline int ll_new_hw_segment(struct request_queue *q,
	280	struct request *req,
	281	struct bio *bio)
	282	{
	283	int nr_hw_segs = bio_hw_segments(q, bio);
	284	int nr_phys_segs = bio_phys_segments(q, bio);
	285
	286	if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
	287	\|\| req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	288	req->cmd_flags \|= REQ_NOMERGE;
	289	if (req == q->last_merge)
	290	q->last_merge = NULL;
	291	return 0;
	292	}
	293
	294	/*
	295	* This will form the start of a new hw segment. Bump both
	296	* counters.
	297	*/
	298	req->nr_hw_segments += nr_hw_segs;
	299	req->nr_phys_segments += nr_phys_segs;
	300	return 1;
	301	}
	302
	303	int ll_back_merge_fn(struct request_queue q, struct request req,
	304	struct bio *bio)
	305	{
	306	unsigned short max_sectors;
	307	int len;
	308
	309	if (unlikely(blk_pc_request(req)))
	310	max_sectors = q->max_hw_sectors;
	311	else
	312	max_sectors = q->max_sectors;
	313
	314	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
	315	req->cmd_flags \|= REQ_NOMERGE;
	316	if (req == q->last_merge)
	317	q->last_merge = NULL;
	318	return 0;
	319	}
2cdf79ca	320	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
d6d48196	321	blk_recount_segments(q, req->biotail);
2cdf79ca	322	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196 JA	323	blk_recount_segments(q, bio);
d6d48196 JA	324	len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
e17fc0a1 DW	325	if (!bio_has_data(bio) \|\|
	326	(BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))
	327	&& !BIOVEC_VIRT_OVERSIZE(len))) {
d6d48196 JA	328	int mergeable = ll_new_mergeable(q, req, bio);
	329
	330	if (mergeable) {
	331	if (req->nr_hw_segments == 1)
	332	req->bio->bi_hw_front_size = len;
	333	if (bio->bi_hw_segments == 1)
	334	bio->bi_hw_back_size = len;
	335	}
	336	return mergeable;
	337	}
	338
	339	return ll_new_hw_segment(q, req, bio);
	340	}
	341
6728cb0e	342	int ll_front_merge_fn(struct request_queue q, struct request req,
d6d48196 JA	343	struct bio *bio)
	344	{
	345	unsigned short max_sectors;
	346	int len;
	347
	348	if (unlikely(blk_pc_request(req)))
	349	max_sectors = q->max_hw_sectors;
	350	else
	351	max_sectors = q->max_sectors;
	352
	353
	354	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
	355	req->cmd_flags \|= REQ_NOMERGE;
	356	if (req == q->last_merge)
	357	q->last_merge = NULL;
	358	return 0;
	359	}
	360	len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
2cdf79ca	361	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	362	blk_recount_segments(q, bio);
2cdf79ca	363	if (!bio_flagged(req->bio, BIO_SEG_VALID))
d6d48196	364	blk_recount_segments(q, req->bio);
e17fc0a1 DW	365	if (!bio_has_data(bio) \|\|
	366	(BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
	367	!BIOVEC_VIRT_OVERSIZE(len))) {
d6d48196 JA	368	int mergeable = ll_new_mergeable(q, req, bio);
	369
	370	if (mergeable) {
	371	if (bio->bi_hw_segments == 1)
	372	bio->bi_hw_front_size = len;
	373	if (req->nr_hw_segments == 1)
	374	req->biotail->bi_hw_back_size = len;
	375	}
	376	return mergeable;
	377	}
	378
	379	return ll_new_hw_segment(q, req, bio);
	380	}
	381
	382	static int ll_merge_requests_fn(struct request_queue q, struct request req,
	383	struct request *next)
	384	{
	385	int total_phys_segments;
	386	int total_hw_segments;
	387
	388	/*
	389	* First check if the either of the requests are re-queued
	390	* requests. Can't merge them if they are.
	391	*/
	392	if (req->special \|\| next->special)
	393	return 0;
	394
	395	/*
	396	* Will it become too large?
	397	*/
	398	if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
	399	return 0;
	400
	401	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
	402	if (blk_phys_contig_segment(q, req->biotail, next->bio))
	403	total_phys_segments--;
	404
	405	if (total_phys_segments > q->max_phys_segments)
	406	return 0;
	407
	408	total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
	409	if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
6728cb0e JA	410	int len = req->biotail->bi_hw_back_size +
6728cb0e JA	411	next->bio->bi_hw_front_size;
d6d48196 JA	412	/*
	413	* propagate the combined length to the end of the requests
	414	*/
	415	if (req->nr_hw_segments == 1)
	416	req->bio->bi_hw_front_size = len;
	417	if (next->nr_hw_segments == 1)
	418	next->biotail->bi_hw_back_size = len;
	419	total_hw_segments--;
	420	}
	421
	422	if (total_hw_segments > q->max_hw_segments)
	423	return 0;
	424
	425	/* Merge is OK... */
	426	req->nr_phys_segments = total_phys_segments;
	427	req->nr_hw_segments = total_hw_segments;
	428	return 1;
	429	}
	430
	431	/*
	432	* Has to be called with the request spinlock acquired
	433	*/
	434	static int attempt_merge(struct request_queue q, struct request req,
	435	struct request *next)
	436	{
	437	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	438	return 0;
	439
	440	/*
	441	* not contiguous
	442	*/
	443	if (req->sector + req->nr_sectors != next->sector)
	444	return 0;
	445
	446	if (rq_data_dir(req) != rq_data_dir(next)
	447	\|\| req->rq_disk != next->rq_disk
	448	\|\| next->special)
	449	return 0;
	450
7ba1ba12 MP	451	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	452	return 0;
	453
d6d48196 JA	454	/*
	455	* If we are allowed to merge, then append bio list
	456	* from next to rq and release next. merge_requests_fn
	457	* will have updated segment counts, update sector
	458	* counts here.
	459	*/
	460	if (!ll_merge_requests_fn(q, req, next))
	461	return 0;
	462
	463	/*
	464	* At this point we have either done a back merge
	465	* or front merge. We need the smaller start_time of
	466	* the merged requests to be the current request
	467	* for accounting purposes.
	468	*/
	469	if (time_after(req->start_time, next->start_time))
	470	req->start_time = next->start_time;
	471
	472	req->biotail->bi_next = next->bio;
	473	req->biotail = next->biotail;
	474
	475	req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
	476
	477	elv_merge_requests(q, req, next);
	478
	479	if (req->rq_disk) {
6f2576af JM	480	struct hd_struct *part
6f2576af JM	481	= get_part(req->rq_disk, req->sector);
d6d48196 JA	482	disk_round_stats(req->rq_disk);
d6d48196 JA	483	req->rq_disk->in_flight--;
6f2576af JM	484	if (part) {
	485	part_round_stats(part);
	486	part->in_flight--;
	487	}
d6d48196 JA	488	}
	489
	490	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
	491
	492	__blk_put_request(q, next);
	493	return 1;
	494	}
	495
	496	int attempt_back_merge(struct request_queue q, struct request rq)
	497	{
	498	struct request *next = elv_latter_request(q, rq);
	499
	500	if (next)
	501	return attempt_merge(q, rq, next);
	502
	503	return 0;
	504	}
	505
	506	int attempt_front_merge(struct request_queue q, struct request rq)
	507	{
	508	struct request *prev = elv_former_request(q, rq);
	509
	510	if (prev)
	511	return attempt_merge(q, prev, rq);
	512
	513	return 0;
	514	}